Method of making lead nitratohypophosphite



Patented May 28, 1940 PATENT OFFICE METHOD OF MAKING LEAD NITRATO- nrrornosrrn'rn Willi Brun, Bridgeport,

Conn., assignor to Remington Arms Company, Inc., a corporation of Delaware N Drawing. Application July 24, 1937, Serial No. 155,449

6 Claims.

This invention relates to the manufacture of double salts of the acids of nitrogen and phosphorous and particularly to the preparation of salts which appear to be combinations of a salt of nitric acid and a salt of hypophosphorous acid.

In an application filed concurrently herewith the present inventor has described the preparation and use of a group of compositions of matter resulting from the reaction of calcium nitrate, lead nitrate, or mercurous nitrate with a hypophosphite of ammonium, potassium, sodium, calcium, strontium, barium, manganese, or lead. The compositions of matter described in said application are secured by precipitation from saturated solutions of the nitrate and the hypophosphite or by the moistening of a dry mixture of the nitrate and the hypophosphite.

The present invention comprises the discovery of another method of producing such nitrato hypophosphites. By way of illustration there will be described the preparation of a double salt of lead nitrate and lead hypophosphite, which, following accepted nomenclature, will be called lead nitrato hypophosphite.

Lead hypophosphite can be made by precipitation induced by the reaction of an unsaturated solution of calcium hypophosphite with an unsaturated solution of lead nitrate. In actual practice the calcium hypophosphite solution has a concentration of between 4 and 15%, preferably about 11%. The concentration of the lead nitrate solution may vary between such limits as and 6 a concentration of about 30% 35 being preferred. When such solutions are brought together with the reacting materials in molecular proportions the yield of lead hypophosphite is only about 70% of the theoretical yield. Increasing or decreasing the amount of lead nitrate by as much as 10% does not vary the yield by more than 2%. It thus appears that the liquor remaining after the precipitate of lead hypophosphite has been filtered off contains substantial amounts of calcium hypophosphite and 45 of lead nitrate which have not entered into the reaction which forms lead hypophosphite.

It has been discovered that if the liquor from which a precipitate of lead hypophosphite has been removed is concentrated to or near the point of saturation and cooled, a second precipitate comes out which is of a wholly different character from the first precipitate, consisting chiefly of the double salt, lead nitrato hypophosphite. The precipitate contains a small amountof calcium, probably as calcium nitrate. For the formation of the double salt it is necessary that the solution be substantially saturated. When lead hypophosphitehas been first precipitated from solutions of the concentration above mentioned not less than 50% of the liquor must be evapo- 5 rated oil? and the remainder cooled.

It is extraordinary and believed to be without precedent that the concentrating of a liquor from which an incomplete yield of a precipitate has been removed should result in a second precipitate of a compound which is distinct and different from the first precipitate. Ordinarily under these conditions concentration of the liquor results merely in securing additional quantities of the first precipitate. Precipitation of the double salt appears to depend upon close molecular proximity. The mixing of solutions of lead nitrate and calcium hypophosphite saturated and at room temperature yields a first precipitate of lead hypophosphite, the same as unsaturated solutions. However, if solutions of lead nitrate and calcium hypophosphite are prepared, saturated at temperatures approaching their boiling points, and brought together in the requisite proportions, the first precipitate is the double salt; no material quantity of lead hypophosphite being precipitated. It appears that if solutions of these two salts react under conditions or substantial molecular separation up to 70% of the theoretical yield of lead hypophosphite is precipitated first but if they react under conditions where the molecules are in relatively close proximity the double salt is formed.

Applicants invention comprises the discovery of a reaction in which concentration of a liquor from which an incomplete yield of a precipitate of a certain compound has been removed results in a second precipitate of a different compound, and the appended claims are to be broadly construed.

What is claimed is:

1. The method of preparing a nitrato hypophosphite which comprises the admixing of unsaturated solutions of a nitrate and a relatively soluble hypophosphite, the precipitation and removal of a relatively insoluble hypophosphite, .the evaporation of the remaining liquor to saturation and the precipitation and removal of a nitrato hypophcsphite.

2. The method of making lead nitrato hypophosphite which comprises the admixture of unsaturated solutions of lead nitrate and calcium hypophosphite, the precipitation and removal of lead hypophosphite, the concentration of the re- 55 maining liquor by evaporation and the subsequent precipitation of lead nitrato hypophosphite.

3. In the preparation of lead nitrato hypophosphite the method which comprises the admixture of unsaturated solutions of lead nitrate and calcium hypophosphite, the precipitation and removal of lead hypophosphite, the concentration to saturation of the remaining liquor and the precipitation and removal of lead nitrato hypophosphite.

4. The method of making lead nitrato hypophosphite which comprises the admixture of solutions of lead nitrate and calcium hypophosphite, the precipitation and removal of lead hypophosphite, the concentration of the remaining liquor by evaporation and the subsequent precipitation of lead nitrato hypophosphite.

5. The method of making lead nitrato hypophosphite which comprises the admixture of solutions of lead nitrate and calcium hypophosphite, the precipitation and removal of lead hypophosphite, the concentration of the remaining liquor by evaporation, and the cooling of the concentrated liquor to precipitate lead nitratohypophosphite.

6. The method of making lead nitrato hypophosphite which comprises the admixture of unsaturated solutions of lead nitrate and calcium hypophosphite, the precipitation and removal of lead hypophosphite, the concentration of the remaining liquor by evaporation and the cooling of. the concentrated liquor to precipitate lead nitratohypophosphite.

WILLIE BRUN.

' CERTIFICATE OF CORRECTION. Patent No. 2,202, 6&6. M y 28, wh

wILLI BRUN.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 1, second column, line 50, for "or substantial" read --of substantial-; and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Office. I

Signed and sealed this 50th day of July, A. D. 191w.

- Henry Van Arsdale, (Seal) Acting Commissioner of Patents 

